This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-26028, filed on Feb. 1, 2001; the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention generally relates to a magnetoresistance effect element and a method for producing the same.
2. Description of Related Art
In recent years, the density of information recorded in a magnetic recording medium has been increased. In HDD (Hard Disk Drive) units, a system having a high packing density of 10 Gbpsi (Gigabit per square inch) has been put to practical use, and a system having a higher packing density has been required. As a countermeasure thereto, it is important to form a narrow track having a width of 1 xcexcm in a magnetic head. Also in a recording and/or reproducing thin-film magnetic head, various proposals for structure have been made in order to achieve a narrow track. However, it is said that a magnetic packing density capable of being applied to the structure of a conventionally proposed recording and/or reproducing thin-film magnetic head is limited to about 100 to 200 Gbpsi. In order to further increase the magnetic packing density, it is required to provide a magnetic gap having a size of 0.1 xcexcm or less and a high reproducing output. However, it is very difficult to realize such a magnetic gap and a high reproducing output in a conventionally proposed recording and/or reproducing thin-film magnetic head.
Therefore, in order to solve these problems, a horizontal thin-film magnetic head and a CPP (Current Perpendicular to the Plane) type magnetoresistance effect film material having a large magnetoresistance effect have been proposed in Japanese Patent Laid-Open Nos. 11-120509 and 11-25433 and Outline of 24-th Lecture of Japan Applied Magnetism Institution (2000), page 427.
FIG. 5 is a schematic diagram most simply showing a CPP type magnetoresistance effect element (which will be also hereinafter referred to as a CPP element). That is, this CPP element 40 has a structure wherein a bottom electrode 41 and a top electrode 45 are formed on the top and bottom of a CPP type magnetoresistance effect film 43, an insulator (not shown) being formed around the bottom and top electrodes 41 and 45. Because of such a structure, a reproducing current I caused to flow through the bottom electrode 41 is separated into a current I1 flowing through the CPP type magnetoresistance effect film 43 and a leakage current I2 flowing between the top and bottom electrodes 41 and 45 to flow into the top electrode 45. At this time, with respect to the output of the CPP type magnetoresistance effect film 43, only a variation in resistance due to the current I1 is detected as a variation in voltage.
In the thin-film magnetic head using the CPP element 40 wherein a current is applied in a direction perpendicular to the plane of the film, the thickness of the insulator decreases as the thickness of the reproducing element (CPP element) decreases. In accordance therewith, the distance between the electrodes 41 and 45 for sandwiching the reproducing element therebetween decreases, and the possibility of increasing a leakage current flowing through the insulator other than a current flowing through the reproducing element increases. Therefore, in order to solve such a problem, it is required to develop a CPP type magnetoresistance effect film material capable of obtaining a high reproducing output with a small current and an insulating material having a high withstand voltage. However, it is not easy to achieve the purposes therefor.
FIG. 6 shows the cross-sectional structure of an actual reproducing magnetic head when the CPP element 40 is applied to the head. In the construction of the reproducing magnetic head, magnetization information is sucked up from a medium (not shown) by a reproducing magnetic yoke 48 to be propagated to the CPP element 40, and the resistance changes by the change in direction of magnetization at that time. In FIG. 6, a magnetization fixing layer 47 is formed on the side portion of the CPP type magnetoresistance effect film 43. Also in this case, in FIG. 6, when a reproducing current is caused to flow, the direction of magnetization of the CPP element 40 fluctuates by a magnetic field due to current from a corner portion of the top electrode 45, so that it is not possible to obtain a high reproducing output.
On the other hand, as a magnetoresistance effect element using the same principle as that of the CPP element, there is a TMR (Tunneling Magneto-Resistance) element. In the case of the TMR element, an insulator of Al2O3 or the like is used as a junction. Since this insulator has a very small thickness of about 1 nm, it is not required to cause a sense current, which flows through the TMR element, to be larger than that of the CPP element, and it is not required to increase the withstand voltage of a surrounding insulator in the TMR element.
On the other hand, it is required to cause a large sense current to flow through the CPP element 40 in order to obtain a high reproducing output. In this case, the magnetic field due to sense current is very large to disturb the direction of magnetization of the magnetization fixing layer 47 and to form the CPP type magnetoresistance effect film 43. Since the direction of magnetization of a magneto-sensitive layer having magnetization disperses, there is a problem in that the detection sensitivity greatly decreases. As an example, the relationship between the sense currents of a TMC element and CPP element and the magnetic fields due to the currents is shown in FIG. 7. As shown in FIG. 7, in order to obtain a necessary and sufficient reproducing output, the sense current of the CPP element must be about ten times as large as that of the TMR element. In accordance therewith, the magnetic field due to current, which is applied to the CPP element and which is produced in the vicinity of the CPP element is a very large magnetic field of 50 to 1000 times as large as that of the TMR element.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a magnetoresistance effect element which is capable of causing a large sense current to flow between electrodes and which has a smaller dispersion in direction of magnetization of a CPP element based on a magnetic field due to the sense current and has a lager reproducing output, and a method for producing the same.
In order to accomplish the aforementioned and other objects, according to a first aspect of the present invention, there is provided a method for producing a magnetoresistance effect element comprising: after forming a first electrode, forming a magnetoresistance effect film on the first electrode; applying a self-condensing organic resist on the magnetoresistance effect film, and thereafter, causing the organic resist to be droplets; subsequently, forming an insulating film thereon, and thereafter, removing the organic resist to form a groove portion in the insulating film to expose the top surface of the magnetoresistance effect film; and filling the groove portion with an electrode material to form a second electrode.
According to such a method for producing magnetoresistance effect according to the first aspect of the present invention, the groove portion formed in the insulating film leaves the magnetoresistance effect film as approaching the periphery of the magnetoresistance effect film, so that the distance between the first and second electrodes increases as approaching the periphery of the magnetoresistance effect film. Thus, even if a large current is caused to flow between the first and second electrodes, it is possible to prevent the direction of magnetization of a magnetization fixing film, which is formed on the side portion of the magnetoresistance effect film, from being disturbed by a magnetic field due to the current, and it is possible to decrease the dispersion in direction of magnetization of the magnetoresistance effect film. In addition, it is possible to decrease a leakage current from the corner portions of the first and second electrodes, so that it is possible to cause a large sense current to flow between the electrodes and obtain a high reproducing output.
Furthermore, for example, the magnetoresistance effect films according to the present invention include giant magnetoresistance effect films and tunneling magnetoresistance effect films which have a ferromagnetic layer, a non-magnetic layer and a ferromagnetic layer and wherein the electric resistance of the whole magnetoresistance effect film varies in accordance with the variation in relative direction of magnetization of the ferromagnetic layers facing each other via the non-magnetic layer. If the non-magnetic layer is a conductive non-magnetic layer of Cu or the like, the magnetoresistance effect film can be widely used as a current perpendicular to the plane type giant magnetoresistance film for a magnetic storage, a magnetoresistance effect head, a magnetic sensor or the like. If the non-magnetic layer contains a dielectric, such as alumina or an oxide film, a tunneling current flows between both ferromagnetic layers via the dielectric, so that the magnetoresistance effect can be widely used as a tunneling magnetoresistance effect film for a magnetic storage, a magnetic head, a magnetic sensor or the like.
According to a second aspect of the present invention, there is provided a method for producing a magnetoresistance effect element comprising: after forming a first electrode, forming a magnetoresistance effect film on the first electrode; forming an insulating film on the magnetoresistance effect film; and using a mask having an opening portion, the position of which matches with the position of the magnetoresistance effect film, to isotropic-etch the insulating film to form a curved recessed portion in the insulating film to expose the top surface of the magnetoresistance effect film to form a second electrode in the recessed portion.
According to such a method for producing magnetoresistance effect according to the first aspect of the present invention, the mask having the opening portion, the position of which matches with the position of the magnetoresistance effect film, is used for isotropic-etching the insulating film formed on the magnetoresistance effect film, so that the curved recessed portion is formed in the insulating film to form the second electrode in the recessed portion. Therefore, the positioning accuracy of the magnetoresistance effect film to the second electrode is improved, and the second electrode having a good shape converging toward the magnetoresistance effect film is obtained, so that the distance between the first and second electrodes increases as approaching the periphery of the magnetoresistance effect film. Thus, even if a large current is caused to flow between the first and second electrodes, it is possible to prevent the direction of magnetization of a magnetization fixing film, which is formed on the side portion of the magnetoresistance effect film, from being disturbed by a magnetic field due to the current, and it is possible to decrease the dispersion in direction of magnetization of the magnetoresistance effect film. In addition, it is possible to decrease a leakage current from the corner portions of the first and second electrodes, so that it is possible to cause a large sense current to flow between the electrodes and obtain a high reproducing output.
Furthermore, the second electrode is preferably formed by forming a converging opening portion, which is communicated with the magnetoresistance effect film, in the insulating film by an anisotropic etching after forming a curved recessed portion, and by filling the opening portion and the recessed portion with an electrode material film.
Thus, since the converging opening portion communicated with the magnetoresistance effect film is formed in the insulating film by the anisotropic etching, the second electrode further converges toward the magnetoresistance effect film, so that it is possible to cause a larger sense current to flow between the electrodes and obtain a larger reproducing output.
According to a third aspect of the present invention, there is provided a magnetoresistance effect element comprising: a first electrode which has a first protruding portion having a substantially flat top face; a current perpendicular to the plane type magnetoresistance effect film, one end of which is electrically connected to the top face of said first electrode; and a second electrode which has a second protruding portion having a substantially flat top face, the second protruding portion being electrically connected to the other end of the magnetoresistance effect film, wherein the first and second protruding portions have shapes converging toward the magnetoresistance effect film in a cross section perpendicular to the film plane of the magnetoresistance effect film.